Oracle reports failure: BEA-101215, Malformed Request

This seems starting from our patching recently, when Oracle reports is called, returns http 400 error intermittently

request url:

http://server:port/forms/java/reports.html?vReportJobID=76588&vReportServer=rep_wls_reports1_orange_asinst_2&vDestination=CACHE

<Oct 26, 2016 4:41:55 PM EST> <Error> <HTTP> <BEA-101215> <Malformed Request "/reports/rwservlet/getjobid=76590". Request parsing failed, Code: -1>

is found in the log.

cleaning java cache and IE history, restart PC, helped some users, but not all of them.

Anyone can give me a hint ?

thank you in advance.

IE 11

Forms/Reports 11.1.2.1.0

Weblogic 10.3.6.0.160719 clustered over 2 nodes

SLES 11